The present disclosure relates to a method for electroplating metal employing a negative electrophoretic photoresist and two lithographic masks, and a structure for implementing the same.
While a positive photoresist or a negative photoresist can be employed to define a cavity for electroplating, commercially available negative photoresists tend to provide better material property such as mechanical adhesion (less brittleness) than commercially available positive photoresists. If a negative type photoresist is employed for the electroplating process, the cavity is defined by blocking light to the area of the cavity during a lithographic exposure.
In ordinary photolithographic processes, mask features include optically opaque areas supported by a transparent glass substrate. Accordingly, opaque areas can sit in isolation on a surface of the transparent glass substrate when such an isolated feature is desired. However, if a physical shadow mask including a metal plate and openings therethrough is used, an isolated light-blocking portion of the metal mask cannot be suspended within the metal plate. In other words, only light-blocking portions of the metal mask that are connected to the remainder of the metal mask can be present as a pattern in the shadow mask.